An airplane is propelled by one or more propulsion assemblies each comprising a turbojet engine housed in a tubular nacelle. Each propulsion assembly is attached to the airplane by a pylon generally located under a wing or at the fuselage.
A nacelle generally has a structure comprising an air intake upstream of the engine, a central section intended to surround a fan of the turbojet engine, a downstream section housing thrust reverser means and intended to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is located downstream of the turbojet engine.
The air intake comprises, on one hand, an air intake lip suitable for allowing optimal collection towards the turbojet engine of the air needed to supply the fan and internal compressors of the turbojet engine, and on the other hand, a downstream structure on which the lip is attached and intended to suitably channel the air towards the blades of the fan. The assembly is attached upstream of the fan casing belonging to the upstream section of the nacelle.
In flight, depending on the temperature and humidity conditions, ice may form on the nacelle, in particular at the outer surface of the air intake lip. The presence of ice or frost alters the aerodynamic properties of the air intake and disrupts the conveyance of air towards the fan. Furthermore, the formation of ice on the air intake of the nacelle and the ingestion of ice by the engine in the event blocks of ice detach can damage the engine, and present a safety risk for the flight.
One solution for defrosting or deicing the outer surface consists of preventing ice from forming on that outer surface by keeping the concerned surface at a sufficient temperature.
Thus, it is known, for example from document U.S. Pat. No. 4,688,757, to take hot air at the turbojet engine compressor and convey it to the air intake lip to heat the walls. However, such a device requires a system of hot air intake pipes between the turbojet engine and the air intake, as well as a system for evacuating hot air at the air intake lip. This increases the mass of the propulsion assembly, which is not desirable.
These drawbacks were able to be offset by using electrical deicing systems.
EP 1 495 963 and a number of other documents relate to electrical deicing and its developments.
In order to lighten the structures used in the composition of nacelles, and more generally, aeronautic equipment, as much as possible, composite materials are used more and more in these structures. The air intake lip of a nacelle can in particular be made from composite materials.
The use of these materials poses certain problems in the context of an electrical deicing device.
Indeed, the exposure temperature of these materials generally must not exceed a critical threshold, subject to distorting the material and therefore damaging the structure. The temperature of the composite material should therefore be monitored so as to avoid any overheating, in particular locally, of the material.
One obvious solution is to equip the structure made from composite material with temperature sensors, typically at least one temperature sensor per heating mat incorporated into the air intake of the nacelle, the air intake having a significant number of heating mats. However, such a solution does not make it possible to avoid certain local overheating between the sensors without substantially increasing the number of temperature sensors used. Such a solution also involves establishing a data transfer network for the data measured by the sensor, which makes the structure heavier and can make the deicing device particularly complex and not very practical in terms of its installation and implementation.
For reliability reasons, it could also be necessary to make the sensors redundant, which would further affect the mass of the structure and increase the complexity thereof.
French application Ser. No. 08/06416 in the applicant's name aims to offset these drawbacks and to do so, referred to a deicing system related to a central control unit of the aircraft (FADEC) so as to obtain information on the outside flight conditions and adapt the deicing power accordingly.
Moreover, combining the electrical power supply and measurement chains for a plurality of resistant mats creates a new problem, i.e. monitoring the integrity of the heating mats.